The purpose of the Pathology and Tissue Resource (PTR) Core is to provide comprehensive histology support, pathology support, and tumor and tissue resources to all five projects of this program. Pathology services will include tissue processing, slide preparation and staining, preparation of tissue arrays, laser capture microdissection, IHC assay development and analysis, in situ hybridization assays, BrdU staining, apoptosis (TUNEL) assays, and confocal microscopy and image analysis. As well as managing and providing access to existing tumor and tissue resources, the PTR Core will also assemble and maintain two new tissue resources that will be used by the projects. One is a retrospective bank of archival paraffin blocks of human invasive breast cancers with clinical follow-up to support prognostic/predictive studies, which will include approximately 2000 cases with extended follow-up, assembled into tissue arrays. The other is a retrospective bank of archival paraffin blocks of human premalignant breast lesions to support studies on the early development and progression to invasive breast cancer ? this bank will include approximately 1200 specimens, also assembled into tissue arrays. Overall, many thousands of blocks and slides will be prepared, stained, and evaluated over the duration of the Program. Performing the work in the PTR Core will ensure that it is done in the most expert, timely, and cost-efficient manner possible.